Merging arguments before using them to select AI service.

Author: Ben Thomas

dotnet/src/Agents/Core/ChatCompletionAgent.cs

@@ -10,6 +10,7 @@
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.SemanticKernel.Agents.Extensions;
+using Microsoft.SemanticKernel.Arguments.Extensions;
 using Microsoft.SemanticKernel.ChatCompletion;
 using Microsoft.SemanticKernel.Diagnostics;
 using Microsoft.SemanticKernel.Services;
@@ -268,7 +269,7 @@ private async IAsyncEnumerable<ChatMessageContent> InternalInvokeAsync(
     {
         kernel ??= this.Kernel;
 
-        (IChatCompletionService chatCompletionService, PromptExecutionSettings? executionSettings) = GetChatCompletionService(kernel, arguments);
+        (IChatCompletionService chatCompletionService, PromptExecutionSettings? executionSettings) = GetChatCompletionService(kernel, this.Arguments.MergeArguments(arguments));
 
         ChatHistory chat = await this.SetupAgentChatHistoryAsync(history, arguments, kernel, additionalInstructions, cancellationToken).ConfigureAwait(false);
 

dotnet/src/Agents/Core/Internal/CoreKernelArgumentsExtensions.cs

@@ -0,0 +1,59 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using System.Linq;
+
+namespace Microsoft.SemanticKernel.Arguments.Extensions;
+
+/// <summary>
+/// Extensions for <see cref="KernelArguments"/>
+/// </summary>
+[ExcludeFromCodeCoverage]
+internal static class CoreKernelArgumentsExtensions
+{
+    private static readonly Dictionary<string, PromptExecutionSettings> s_emptySettings = [];
+
+    /// <summary>
+    /// Provides a merged instance of <see cref="KernelArguments"/> with precedence for override arguments.
+    /// </summary>
+    /// <param name="primaryArguments">Primary arguments to merge. This is the base set of arguments.</param>
+    /// <param name="overrideArguments">The override arguments.</param>
+    /// <remarks>
+    /// This merge preserves original <see cref="PromptExecutionSettings"/> and <see cref="KernelArguments"/> parameters.
+    /// It allows for incremental addition or replacement of specific parameters while also preserving the ability
+    /// to override the execution settings.
+    /// </remarks>
+    internal static KernelArguments MergeArguments(this KernelArguments? primaryArguments, KernelArguments? overrideArguments)
+    {
+        // Avoid merge when override arguments are not set.
+        if (overrideArguments is null)
+        {
+            return primaryArguments ?? [];
+        }
+
+        // Avoid merge when the Agent arguments are not set.
+        if (primaryArguments is null)
+        {
+            return overrideArguments ?? [];
+        }
+
+        // Both instances are not null, merge with precedence for override arguments.
+
+        // Merge execution settings with precedence for override arguments.
+        Dictionary<string, PromptExecutionSettings>? settings =
+            (overrideArguments.ExecutionSettings ?? s_emptySettings)
+                .Concat(primaryArguments.ExecutionSettings ?? s_emptySettings)
+                .GroupBy(entry => entry.Key)
+                .ToDictionary(entry => entry.Key, entry => entry.First().Value);
+
+        // Merge parameters with precedence for override arguments.
+        Dictionary<string, object?>? parameters =
+            overrideArguments
+                .Concat(primaryArguments)
+                .GroupBy(entry => entry.Key)
+                .ToDictionary(entry => entry.Key, entry => entry.First().Value);
+
+        return new KernelArguments(parameters, settings);
+    }
+}